$hextent = $scrollbox->hextent

METHODS

$scrollbox->scroll( $downward, $rightward )

Requests the content be scrolled downward a number of lines and rightward a number of columns (either of which which may be negative).

$scrollbox->scroll_to( $top, $left )

Requests the content be scrolled such that the given line and column number of the child's content is the topmost visible in the container.

SMART SCROLLING

If the child widget declares it supports smart scrolling, then the ScrollBox will not implement content scrolling on its behalf. Extra methods are used to co-ordinate the scroll position between the scrolling-aware child widget and the containing ScrollBox. This is handled by the following methods on the child widget.

If smart scrolling is enabled for the child, then its window will be set to the viewport directly, and the child widget must offset its content within the window as appropriate. The child must indicate the range of its scrolling ability by using the set_total method on the extent object it is given.

$smart = $child->CAN_SCROLL

If this method exists and returns a true value, the ScrollBox will use smart scrolling. This method must return a true value for this to work, allowing the method to itself be a proxy, for example, to proxy scrolling information through a single child widget container.

$child->set_scrolling_extents( $vextent, $hextent )

Gives the child widget the vertical and horizontal scrolling extents. The child widget should save thes values, and inspect the start value of them any time it needs these to implement content offset position when rendering.

$child->scrolled( $downward, $rightward, $h_or_v )

Informs the child widget that one of the scroll positions has changed. It passes the delta (which may be negative) of each position, and a string which will be either "h" or "v" to indicate whether it was an adjustment of the horizontal or vertical scrollbar. The extent objects will already have been updated by this point, so the child may also inspect the start value of them to obtain the new absolute offsets.

TODO

Choice of left/right and top/bottom bar positions.

Click-and-hold on arrow buttons for auto-repeat

Allow smarter cooperation with a scrolling-aware child widget; likely by setting extent objects on the child if it declares to be supported, and use that instead of an offset child window.